Police described the $2,500 necklace on Wednesday as "one of a kind."
Detectives obtained a search warrant Tuesday in the grand theft investigation to search Lohan's Venice home, but before they could, the necklace was returned to the police station, according to an LAPD statement.
Lohan's attorney Shawn Chapman Holley wasn't immediately available for comment.
The actress continues to be on probation and remains under random drug testing in her ongoing DUI case. Lohan, 24, faces a Feb. 25 progress review hearing.
She's also currently under investigation by Riverside County prosecutors for allegedly battering a Betty Ford employee.
L.A. Superior Court Judge Elden Fox previously warned Lohan on Oct. 22 that any more slip-ups would be met with six months in jail.